{"id":365533,"date":"2024-05-04T18:29:19","date_gmt":"2024-05-04T18:29:19","guid":{"rendered":"\/forum\/forums\/topic\/why-dont-the-residuals-converge\/"},"modified":"2024-05-04T18:59:04","modified_gmt":"2024-05-04T18:59:04","slug":"why-dont-the-residuals-converge","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/why-dont-the-residuals-converge\/","title":{"rendered":"Why don&#8217;t the residuals converge?"},"content":{"rendered":"<p>I&#8217;d like to simulate the inflow\/flow around a box. The fluid (air) itself is separated into 2 fluid bodies due to simulations planned for later. The inner body is a sphere, the outer is a cuboid.<br \/><a class=\"wp-colorbox-image cboxElement\" href=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/05\/02-05-2024-1714653565-mceclip0.png\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/05\/04-05-2024-1714849096-mceclip0.png\" width=\"438\" height=\"359\"><\/a><a class=\"wp-colorbox-image cboxElement\" href=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/05\/02-05-2024-1714653565-mceclip0.png\">&nbsp;<\/a><\/p>\n<p><strong>My setup:<\/strong><\/p>\n<p><span style=\"text-decoration: underline\">Meshing<\/span><\/p>\n<ul>\n<li>Box as dead<\/li>\n<li>Inverse Quality: Max = 0.78 (only a few), Average = 0.02<\/li>\n<li>round about 2000000 cells<\/li>\n<li>I&#8217;ve already connected the congruent spherical surfaces of the 2 fluid bodies in the geometry (in SpaceClaim) and it&#8217;s therefore treated as one (in simulation as interface). Therefore I used a conformal mesh.<\/li>\n<li>There is one velocity inlet (left side of the outer fluid body) and one pressure outlet (right side of the outer fluid body). All the other zones are walls.<\/li>\n<li>I answered the following questions as:\n<ul>\n<li>Geometry Type -&gt; The geometry consists of both fluid and solid regions and\/or voids<\/li>\n<li>Change all fluid-fluid boundary types from &#8216;wall&#8217; to &#8216;internal&#8217;? -&gt; Yes<\/li>\n<li>Do you need to apply Share Topology? -&gt; No (Since the 2 spherical surfaces are already treated as one due to the settings in SpaceClaim)<\/li>\n<li>Enable Multizone Meshing? -&gt; No<\/li>\n<li>Will you cap openings and extract fluid regions? -&gt; No<\/li>\n<\/ul>\n<\/li>\n<li>I used a poly-hexcore mesh<\/li>\n<\/ul>\n<p><a class=\"wp-colorbox-image cboxElement\" href=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/05\/02-05-2024-1714653565-mceclip0.png\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/05\/02-05-2024-1714653565-mceclip0.png\" width=\"653\" height=\"331\"><\/a><\/p>\n<p><span style=\"text-decoration: underline\">Solution<\/span><\/p>\n<ul>\n<li>velocity inlet = 13 m\/s<\/li>\n<li>I left the rest of the settings as default&nbsp;\n<ul>\n<li>The congruent spherical surfaces, let&#8217;s say I name them zone1 (from outer fluid body body1) and zone2 (from inner fluid body body2), are listed as&nbsp;<em>Internal<\/em> under&nbsp;<em>Boundary Conditions<\/em> as follows:\n<ul>\n<li>zone1-zone2-body1-body2<\/li>\n<li>interior&#8211;body1<\/li>\n<li>interior&#8211;body2<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<li>The hybrid initialization was done after 10 iterations (with 7.3e-09)<\/li>\n<li>For my first attempt, I set the number of iterations to 1000.<\/li>\n<li>I clicked on&nbsp;<em>Check Case&#8230;<\/em> and it said&nbsp;<em>No recommendations to make at this time.<\/em><\/li>\n<\/ul>\n<p>But after 1000 iterations the scaled residuals are still too high . The whole problem seems not that complex to me, but I am still a beginner and I have absolutely no idea what could be the reason for this. Can anyone help me?<\/p>\n<p><a class=\"wp-colorbox-image cboxElement\" href=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/05\/04-05-2024-1714847326-mceclip0.png\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2024\/05\/04-05-2024-1714847326-mceclip0.png\" width=\"679\" height=\"394\"><\/a> The scaled residuals stayed like this even after 1000 iterations&#8230;<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"template":"","class_list":["post-365533","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_subscription":["292260","199"],"_bbp_author_ip":["23.196.2.143"]," _bbp_last_reply_id":["0"]," _bbp_likes_count":["0"],"_btv_view_count":["274"],"_bbp_topic_status":["unanswered"],"_edit_lock":["1714849018:229002"],"_bbp_topic_id":["365533"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","292260"],"_bbp_voice_count":["2"],"_bbp_reply_count":["2"],"_bbp_last_reply_id":["365860"],"_bbp_last_active_id":["365860"],"_bbp_last_active_time":["2024-05-07 13:34:03"]},"test":"j-sprengeltu-bs-de"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/365533","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":2,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/365533\/revisions"}],"predecessor-version":[{"id":365538,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/365533\/revisions\/365538"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=365533"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}